Optical recording medium and device for reproducing the same
An optical recording medium includes: a substrate on which information is recorded as phase pits, and a polarization state varying layer for rotating a polarization state of a light beam irradiated thereon in accordance with a temperature distribution caused by irradiation of the light beam. A device for reproducing information recorded on the optical recording medium includes: light irradiation unit for irradiating a read-out light beam to produce a light spot on the optical recording medium so that a light intensity of the light beam at a first portion of the light spot is higher than a predetermined level, separation unit for separating a component of light beam having a predetermined polarization state from a light beam reflected by the optical recording medium, light receiving unit for receiving the light beam separated by said separation means and generating read-out signal, and reproducing unit for reproducing information recorded on the optical recording medium on the basis of the read-out signal.
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Claims
1. An optical recording medium for use with a reproduction device having an objective lens with a numerical aperture NA and a light beam with a wavelength.lambda. comprising:
- a substrate layer on which information is recorded as phase pits with a space frequency greater than 2NA/.lambda.; and
- a polarization-state varying layer for rotating a polarization state of the light beam when irradiated thereon in accordance with a temperature distribution of the irradiated light beam, wherein a magnetization state of said polarization-state varying layer varies in accordance with a temperature distribution during an irradiation of said light beam.
2. An optical recording medium according to claim 1, further comprising protection layers for protecting said polarization-state varying layer.
3. An optical recording medium according to claim 1, wherein the polarization state of the light beam is rotated by a magneto-optical effect.
4. An optical recording medium according to claim 1, further comprising a reflection layer.
5. An optical recording medium according to claim 1, wherein said polarization state varying layer comprises a Curie point recording material whose magnetic domain is extinguished at a temperature above the Curie temperature.
6. An optical recording medium according to claim 1, wherein said polarization state varying layer comprises a compensation point recording material whose coercive force increases at a compensation point temperature.
7. An optical recording medium according to claim 1, further comprising a magnetic field applying layer for directing the magnetizing direction of the polarization state varying layer in a single direction.
8. An optical recording medium according to claim 1, further comprising a switching layer coupled to the polarization state varying layer by an exchange-coupling at a temperature lower than a Curie point temperature and a magnetic domain of which is extinguished at a temperature above the Curie point temperature.
9. An optical recording medium according to claim 1, wherein said polarization-state varying layer receives the light beam and forms a first area and a second area having different magnetization states from each other within a portion of the polarization-state varying layer where the light beam is irradiated, said first area and said second area outputting portions of the received light beam as output light beams having different polarization-states from each other.
10. An optical recording medium according to claim 9, wherein said first area and said second area have the same magnetization state when the light beam is eliminated.
11. An optical recording medium according to claim 10, wherein said first area is a high temperature area and said second area is a low temperature area.
12. An optical recording medium for use with a reproduction device having an objective lens with a numerical aperture NA and a light beam with a wavelength.lambda. comprising:
- a substrate layer on which information is recorded as phase pits with a space frequency greater than 2NA/.lambda.; and
- a polarization-state varying layer for rotating a polarization state of the light beam when irradiated thereon in accordance with an intensity distribution of the irradiated light beam, wherein a magnetization state of said polarization-state varying layer varies in accordance with an intensity distribution during an irradiation of said light beam.
13. An optical recording medium according to claim 12, further comprising protection layers for protecting said polarization-state varying layer.
14. An optical recording medium according to claim 12, wherein the polarization state of the light beam is rotated by a magneto-optical effect.
15. An optical recording medium according to claim 12, further comprising reflection layer.
16. An optical recording medium according to claim 12, wherein said polarization state varying layer comprises a Curie point recording material whose magnetic domain is extinguished at a temperature above the Curie temperature.
17. An optical recording medium according to claim 12, wherein said polarization state varying layer comprises a compensation point recording material whose coercive force increases at a compensation point temperature.
18. An optical recording medium according to claim 12, further comprising magnetic field applying layer for directing the magnetizing direction of the polarization state varying layer in a single direction.
19. An optical recording medium according to claim 12, further comprising a switching layer being coupled to the polarization state varying layer by an exchange-coupling at a temperature lower than a Curie point temperature and magnetic domain of which is extinguished at a temperature above the Curie point temperature.
20. An optical recording medium according to claim 12, wherein said polarization-state varying layer receives the light beam and forms a first area and a second area having different magnetization states from each other within a portion of the polarization-state varying layer where the light beam is irradiated, said first area and said second area outputting portions of the received light beam as output light beams having different polarization-states from each other.
21. An optical recording medium according to claim 20, wherein said first area and said second area have the same magnetization state when the light beam is eliminated.
22. An optical recording medium according to claim 21, wherein said first area is a high temperature area and said second area is a low temperature area.
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Type: Grant
Filed: Jul 24, 1996
Date of Patent: Jun 2, 1998
Assignee: Pioneer Electronic Corporation (Tokyo-to)
Inventors: Nobuaki Onagi (Tsurugashima), Takanobu Higuchi (Tsurugashima)
Primary Examiner: Leszek Kiliman
Law Firm: Kane,Dalsimer,Sullivan, Kurucz, Levy, Eisele and Richard, LLP
Application Number: 8/685,768
International Classification: G11B 566;
